Process of drilling wells using retarded set cement and slurries thereof



UNITED STATES PATENT OFFICE PROCESS OF DRILLING WELLS USING RETARDED sa'r CE ENT' ND'SLUR- ms THEREOF Herman H. Kaveler, Bartlesville, kla., asslgnor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Original application December 27,

1949,Serial No. 135,313. Divided and this application December 29, 1-952, Serial l\ lo.-2 8 ,5 00

4 Qlaims. (CL 166- 22) t rded rates of set, or thickening time. In one contains 2 to 4 carbon atoms in the amount -o aspect it relates to aqueous slurries of such 0.05% vto 5% but preferably about 1% based on cement. In one. aspect it relates to methcdsof the .weightiof dry cement and preferablyusing making these slurries. This application is a s ordinary. commercial Portland cement-containdivision of mycopendlng application Serial No. ing the usual additives, along-with sufllcient 135,313, filed December 27, 1949, now Patent No. waterto .make a slurry, that the water loss as 2, 29,6 7. which cop nding application is a condetermined byfiltration tests is greatly reduced tinllation-in-part oi application Serial No. 47.555, and contamination of the formation is substanfiled September 2,' 1948, now abandoned. In 10 tialiy prevented.

This invention relates to cements having .re- .to 4...ee,rb n atom nd the hydroxyalkyl group another aspect it relates to retarded set cement One object of the present invention is to proslurries comprising hydraulic cement, such as vide an improved cement slurry useful in rout- Portland cement, with or without non-cementing in general, in cementing the walls of wells.

ing inert granular aggregate material, which and for cementing pipe in wells. hydraulic cement mayor may not contain the -Another objectis to. provide a retarded set usual minor additives to hydraulic cements such cement.

as calcium sulfate and/or calcium chloride as an Another object .is to provide a cement slurry example in the usual amounts, a small but efiechaving a high compressive strength suitable for tive amount of a set retarding agent Qgmnrismg use in oil well cementing operations. essentiadly allgyl ydroxyalk lacellul se4,mixed 0 Numerous other objects and advantages will arses where thejalkyl group contains 1 to 4 car-- be apparent upon reading the accompanying :1 atoms and the hydroxyalkyl group contains specification and claims.

2 to 4; carbon atoms, and suflicient water to In preparing the slurry the dry ingredients makeaslurry. comprising hydraulic cement, with or without In the cementing of oil wells it is customary the usual additives, the inert filler material, such to mix ahydraulic cement, for example a Portas sand or crushed limestone, and the alkyl hyland or Portland type cement, with the requisite droxyalkyl cellulose mixed ethers where the alkyl amountof water to form. a Dumpable neat slurry, group contains 1 to 4 carbon atoms and the and to pump the mixture into the well and down hydroxyalkyl group contains 2 to 4 carbon atoms the hole into the place where it is desired to have :-:n may .be mixed together and later mixed with it harden. In present oil well drilling practice, water, or any of them may be mixed separately with wells commonly ranging from 6,000 to 12,000 with water, and then mixed together to form feet or more in depth, high temperatures are the cement slurry, as long as the mixing of the encountered at the locations which are to be hydrauliccement with waterisdone promptly cemented, and relatively long periods of time are before placing the slurry in position. a often required to pump the slurry into place. By hydraulic .cement I intend to include all Furthermore, in the customary practice of pump mixtures of lime, silica, and alumina, or of lime the cement slurry down through the casing and magnesia, silica, and alumina and iron oxide and either forcing it upward around the outer (magnesia, for example, may replace partof the surface of the casing orthrough perforations in 4b lime, and iron oxidea part ofwthe alumina) as the lower end of th'casin'g into the formation are commonly lsnown as hydraulic cements. sought to be sealed, the slurry is required to pass Hydraulic cements include hydraulic limes, grapthrough narrow channels and small openings. pier cements, puzzalan cements,-natural cements, 5 Successful placement of the slurry, therefore,. reand Bertieno, cements. .luzzalan cements inquires that the slurry shall remain fluid and 4:; elude sla-geementsmade irom .slaked lime and pu pab e at hi htemperfleslrhflseveralhgiirrs granulated blast furnaeeslag. Because of its before itll ieg i'nsf'tollarden. However, after the superior strength Portland cement is preferred slu" been pumped into place, it is desirable among the hydraulic 'cements,l'but as the art of to have the hydration or set proceed at a 'rate cements recognizes hydraulic cements as a dellat which .the slurry will attain its final set and so niteclasaand as-resultsof value may. be obdevelop considerablestrength within about 24 waa nynemberpr that class/it is deliours. sired to claim all'hiidr mic-cements. E-PWE Q QQ-PMP X easi s sm ll but. amest-e11. tive amount of, allgyl yqroxyalky e atroiis'it egr ss-1y;

PILLS-Lisible to add any desired amount of an inert granular filling material or aggregate such as sand, ground limestone, or any of the other well known inert aggregates, as long as the amount added does not reduce the strength below the desired value. In operations in open wells it is often desirable to use neat cement, because inert filling material will automatically become detached from the walls of the well, and will tend to mix with and.dilute the slurry to such an extent that it is undesirable to'add any fillin material to the slurry being forced into the well.

The amount of water added is not critical, it being obvious that suflicient water should be added to form a pumpable slurry, and that when the slurry becomes pumpable no further water need be added. One advantage of the slurry of the present invention is that it is a low viscosity, retarded set slurry. Another advantage is its increased compressive strength.

For the purpose of illustrating the material with a formula, cellulose may be regarded as consisting of a number of glucoside residues X, each having three hydroxyl radicals -OH thereon. The residue X is repeated a large number of times, represented by n, which may be 100 or more. Most of the OH radicals are unchanged, but a desired number of them are substituted. There can be from one to three substitutions on each glucoside residue as there are three hydroxyl groups thereon. I prefer a substitution of alkyl groups for the hydrogen of these three hydroxyl groups between 0.05 and 2.25 and more preferably from 0.1 to 1.75 per glucoside residue unit as an average substitution. These two preferred ranges of substitution are similarly preferred for the average amount of substitution of the hydroxyalkyl groups for the hydrogen groups in the glucoside units of the cellulose, but obviously the sum of the two substitutions must be less than a total of three. Alkyl groups, such as methyl groups. attached to cellulose tend to make it water-soluble while the hydroxyalkyl groups have great dispersive powers in addition, and it is believed the combination of these two functions of these alkyl and hydroxyalkyl groups when both are attached to the cellulose makes superior cement slurry set retarding agent than if only one group were present. The alkyl radical CmH2m+l where m is an integer from 1 to I 4, inclusive, replaces some of the hydrogen atoms in the OH radicals of the celluloses and the hydroxyalkyl radical CyH21 OH where y is an integer from 2 to 4, inclusive, replaces the hydrogen in other of the OH radicals, not necessarily attached to the same residue X, but to some residue X of the same cellulose molecule, to the desired extent. The formula therefore is represented as follows:

In the case of the preferred material, methyl hydroxyethyl cellulose, this would be:

/O.CH: [X OCH:GH:OH]

on The compounds covered are methyl, ethyl or propyl, hydroxyethyl, hydroxypropyl or hydroxybutyl cellu ose mixed ethers.

The preparation of methyl hydroxyethyl cellu lose was 'made in the following mannerfi Alkali cellulose was prepared by adding 1 liter of 32% sodium hydroxide solution to grams of Chem-Cotton and allowing the cotton to mercerize for 2 hours. The excess liquid was removed in a bucket centrifugal filter. The alkali cellu lose was then air dried. The dry alkali cellulose was charged to a one liter stainless steel bomb. The bomb was evacuated to 20 mm., then brought to atmospheric pressure with methyl chloride. The bomb was re-evacuated to 40 mm. pressure and 13 grams of ethylene oxide were added at 69 F. The pressure increased, then reduced to 640 mm. This was allowed to stand overnight. Methyl chloride was added to bring the gage pressure to 60 pounds per square inch. The bomb was heated to 176 F. and the temperature maintained essentially constant (:5" F.). Additional methyl chloride was added when the pressure dropped to 40 pounds per square inch gage. No pressure drop was obtained after four hours and reactions were presumed to be complete.

The crude methyl hydroxyethyl cellulose, a light brown powder, was purified by three successive acetone precipitations of water solutions of the cellulose derivative. A total of grams of purified methyl hydroxyethyl cellulose were recovered. The viscosity of a 1% aqueous solution was 1 cps. at 20 C. and the pH was 12.5.

Methyl bromide, ethyl and propyl chloride or bromide and butyl bromide may be employed in the above procedure in place of the methyl chloride to attach the corresponding alkyl groups to, the cellulose, while halogen hydrins of poly-alcohols may be employed in place of the ethylene oxide to form the corresponding hydroxyalkyl celluloses. Glycol chlorohydrin reacts with alkali cellulose to form hydroxyethyl cellulose and glycerol a-monochlorohydrin reacts to form dihydroxypropyl cellulose, and higher hydroxyalkyl celluloses are similarly prepared.

I have found that from 0.05% to 5% of alkyl hydroxyalkyl cellulose mixed ethers where the alkyl group contains 1 to 4 carbon atoms and the hydroxy-alkyl group contains 2 to 4 carbon atoms are particularly efiective in increasing the time of set of hydraulic cement aqueous slurries, with or without inert filling material present.

A Portland cement slurry was made up weighing fifteen pounds to the gallon of slurry (about 53 grams of water per 100 grams of cement) and 1% of methyl hydroxyethyl cellulose mixed ether by weight (based on the dry Portland cement) was added to one-half of the sample. The two halves of the sample were tested separately according to the test procedure for drilling muds described in A. P. I. code 29 and for cements in A. P. I. code 32 (time of set with Vicat apparatus under section X). The results of the tests are tabulated as follows:

" Methyl hydroxyethyl cellulose mixed ether.

The methyl, ethyl, propyl and butyl radicals are substantially equivalent in these mixed ethers andall give beneficial resul It is also obvious that inert filling material will 5 not substantially aifect the result of this test when used in an amount not large enough to deleteriously reduce the strength of the cement slurry after setting.

The above tests are given for illustrative purposes and should not be regarded as limiting the invention, the scope of which is set forth in the following claims.

I claim:

1. The process of cementing a well which extends into a porous formation which comprises placing a hydraulic cement aqueous slurry having a reduced water loss adjacent to said porous formation by admixing with hydraulic cement from 0.1 per cent to 3 per cent by weight of the dry cement of at least one of the group consisting of alkyl hydroxyalkyl cellulose mixed ethers Where the alxyl group contains 1 to 4 carbon atoms and the hydroxyalkyl group contains 2 to 4 carbon atoms, which are soluble in the cement slurry, interacting therewith suflicient water to produce a fluid slurry, and introducing said slurry into said well into contact with said porous formation.

2. The process of cementing a well which extends into a porous formation which comprises placing a hydraulic cement aqueous slurry having a reduced water loss adjacent to said porous formation by admixing with hydraulic cement a minor proportion effective to reduce the water loss of said slurry of at least one of the group consisting of alkyl hydroxyalkyl cellulose mixed ethers where the alkyl group contains 1 to 4 carbon atoms and the hydroxyalkyl group contains 2 to 4 carbon atoms, which are soluble in the cement slurry, interacting therewith suflicient water to produce a fluid slurry, and introducing said slurry into said well into contact with said porous formation.

3. The process of cementing a well which extends into a porous formation which comprises placing a hydraulic cement aqueous slurry having a reduced water loss adjacent to said porous formation by admixing with hydraulic cement from 0.1 per cent to 3 per cent by weight of the dry cement of methyl hydroxyethyl cellulose mixed ether which is soluble in the cement slurry, interacting therewith sufficient water to produce a fluid slurry and introducing said slurry into said well into contact with said porous formation.

4. The process of cementing a well which extends into a porous formation which comprises placing a hydraulic cement aqueous slurry having a reduced water loss adjacent to said porous formation by admixing with hydraulic cement a. minor proportion eifective to reduce the water loss of said slurry of methyl hydroxyethyl cellulose mixed ether which is soluble in the cement slurry, interacting therewith sufi'icient water to produce a fluid slurry and introducing said slurry into said well into contact with said porous formation.

HERMAN H. KAVELER.

Name Date Kaveler Feb. 24, 1953 Number 

1. THE PROCESS OF CEMENTING A WELL WHICH EXTENDS INTO A POROUS FORMATION WHICH COMPRISES PLACING A HYDRAULIC CEMENT AQUEOUS SLURRY HAVING A REDUCED WATER LOSS ADJACENT TO SAID POROUS FORMATION BY ADMIXING WITH HYDRAULIC CEMENT FROM 0.1 PER CENT TO 3 PER CENT BY WEIGHT OF THE DRY CEMENT OF AT LEAST ONE TO THE GROUP CONSISTING OF ALKYL HYDROXYALKYL CELLULOSE MIXED ETHERS WHERE THE ALKYL GROUP CONTAINS 1 TO 4 CARBON ATOMS AND THE HYDROXYALKYL GROUP CONTAINS 2 TO 4 CARBON ATOMS, WHICH ARE SOLUBLE IN THE CEMENT SLURRY, INTERACTING THEREWITH SUFFICIENT WATER TO PRODUCE A FLUID SLURRY, AND INTRODUCING SAID SLURRY INTO SAID WELL INTO CONTACT WITH SAID POROUS FORMATION. 